Problems associating vertebrates to a specific gro

Is difficult to classify, but is closer to being a mammal than any of the four other verebrate groups

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How animals are adapted for survival - dry/cold ar

Due to many factors:

Changes to surface area => heat/water transfer factor => desert animals tend to have a large surface area/volume ratio => allow excess body heat to be readily lost. This helps overheating, partially as they do not sweat as much and produce smaller volumes of conc. urine

Changes to surface area => Animals in colder areas have a smaller surface area/volume ratio to reduce heat loss to minimise heat loss

Amount of body fat => Arctic animals have layers of fat/blubber => minimises heat loss AND acts as an energy store (has a very high calorific value)

Camoflage => Desert animals have sand-coloured coats => good for hiding from predators

Camoflage => Arctic animals have white fur to blend in with the arctic background => increases chances of killing

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Darwin's theory of natural selection

variation – most populations of organisms contain individuals which vary slightly from one to another, those with superior characteristics are more likely to survive,

b) over-production – most organisms produce more young than will survive to adulthood ensuring some will survive,

c) struggle for existence – because populations do not generally increase rapidly in size there must therefore be considerable competition for survival between the organisms,

d) survival - those with advantageous characteristics are more likely to survive this struggle,

e) advantageous characteristics inherited – better adapted organisms are more likely to reproduce successfully passing on the advantageous characteristics to their offspring

f) gradual change – over a period of time the proportion of individuals with the advantageous characteristics in the population will increase compared with the proportion of individuals with poorly adapted characteristics, and the poorly adapted characteristics may eventually be lost.

Continuous variation is when a particular characteristic of an individual lies within a range with no distinct category.

Discontinuous variation occurs when a particular characteristic of the species fits into a few particular and specific categories with no range of variation.

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How speciation occurs

A species is group of similar organisms that can interbreed to give fertile offspring.

Speciation is the development of a new species and can happen when populations of the same original species becomes so different (genetically) that they can no longer interbreed to give fertile offspring.

Speciation can occur via isolation – two populations of a species become separated, eg geographically,

In the two geographical regions, the climate might be different, the other plants and animals may be different.

However, if each population can survive, by the process of natural selection, two distinct species can evolve (or perhaps one population remains the same, but the other has to adapt to a different environment).